Former world champion boxer Keith Thurman acknowledged his confidence took a hit when he lost to Manny Pacquiao last year.

As a result, Thurman lost his drive to train.

Compounding the issue was his need to rest his left hand, which needed to be operated on after the fight.

This is why the former 147-pound champion ballooned to 190 pounds.

“After the hand injury, I was 192 pounds. That was last (late) summer when I was commentating on the Spence vs. Porter fight," Thurman said in an interview posted on Fight Hype.

“I was depressed. I didn’t enjoy taking my first career, L, even though I lost to a champion (Manny Pacquiao)."

• Boxing: Pacquiao outpoints Thurman, gains WBA welterweight belt

Thurman said he is currently working on shedding off weight so he can get back to training shape.

“Right now, I am 171 pounds. I have been for the last 3 weeks. I’ve been neglecting the cardio, so it’s no more," he said.

“I want to see the numbers change, and I want to get down to my amateur weight close to 165 or 160 pre-camp."

Thurman said he still wants to get back at Pacquiao again to recover the WBA "super" welterweight title.

• Boxing: No Thurman rematch as Pacquiao eyes other welterweights

"You know I loved that last Pac fight. I love you, too. I still want my get back. I really want to get back, get back healthy, get back strong. Get back focused," he said.

Thurman entered the Pacquiao bout undefeated in 30 fights.

The Filipino caught a backpedalling Thurman with a right hand, dropping the American late in the first round.

Thurman regained his composure in the middle rounds, only to be hurt with a vicious left hook to the body.

In the end, Pacquiao won via split decision to become the oldest welterweight to win a major title at 40.